Many electric clothes dryers have an automatic setting for the purpose of terminating the cycle when the clothes are dry, to save energy. However, many of the dryers now in use do not have this feature, and independent tests indicate that many models incorporating automatic termination still overdry the clothes, thereby wasting up to 20% of the electricity or more.
Conventional automatic termination systems in dryers today may use the dryer temperature or the humidity of the air or the electrical conductivity of the load itself to determine when to terminate the cycle. Frequently, the decision is made by allowing a given amount of heater-on or heater-off time to elapse after a predetermined threshold is reached. This elapsed time is usually determined by a user set point on the control dial of the dryer.
Consumer reports and tests by others indicate that while these automatic shut-off mechanisms are somewhat effective, they frequently overdry the loads, in many cases running longer than necessary, after the load is dry. This not only wastes energy, but it causes unnecessary wear on the fabric and to the dryer itself.